This invention relates to a flow machine and more particularly this invention relates to a turbopump or flow meter device having an impeller which provides a passage for an agressive, radioactive or special-purity flow medium and is radilly supported in the interior of the machine casing. This impeller is in most instances radially supported over its radially extreme circumferential area. The aggressive flow medium may be, f.i., an acid or one for the chemical or pharmaceutical industry, where the conveyance of extremely pure flow media is a frequent requirement.
Turbomachines of this general type have been contemplated where the flow duct of the machine, or an axial impeller bore connected to the flow duct for the passage of the flow medium, communicates with the bearing gap or bearing gaps of the radially arranged bearing during operation of the machine and where this flow medium serves as a bearing lubricant. The disadvantage affecting this solution is that such a flow medium is very often ill-suited as a bearing lubricant generally or at least in many instances is ill-suited for the particular bearing or the material of its running surface. For example, numerous materials used for running surfaces are subject to attack by certain aggressive flow media.
Likewise a vertically arranged rotor has been contemplated which is restrained or axially supported by the attraction of a magnet arranged at its upper end.
A broad object of the present invention is to obviate the use of the flow medium as a bearing lubricant and equally to eliminate the necessity for a seal between the bearing gap and the flow area for preventing mutual contact or mixing of the flow medium with a bearing lubricant or contact of a bearing running surface material with the flow medium.
It is a particular object of the present invention to provide a flow machine where the radial bearing is free from mechanical contact by means of a magnetic device. The flow medium is here not used as a lubricant. The bearing properties may then be independent of the properties of the flow medium. Bearing lubricants, such as a liquid, are eliminated altogether. Special material for bearing running surfaces is not necessary since the bearing is free from contact, friction and wear, and the material can also not be attacked by the flow medium. Further, the need for said seal is eliminated in that sealing problems of this nature are removed. Mutual contact or mixing of a said flow medium with a bearing lubricant, such as a bearing oil, cannot take place; contamination of either medium by the other medium, mutual contamination or mutual chemical reactions are impossible. The aggressive, radioactive or special-purity flow medium may be allowed to dwell in or pass through the bearing gap. There is no need for keeping it away from the bearing gap. Nor does the impeller bearing require servicing.
Except to the inlet and outlet flow of the aggressive or similar flow medium the casing of the machine may be closed off against the outside. Shaft lead-ins in the casing to accommodate outboard bearings can be eliminated. Sealing problems connected therewith are likewise prevented. Inasmuch as a centrally arranged impeller shaft can be eliminated, the inlet area can be enlarged where the flow into the impeller is axial to it, which is of particular benefit to turbo processing machines.
The flow machine cited in the present invention is most often a turbo processing machine, more particularly a turbopump, or a turbine. This may be an axial-flow turbomachine, mixed-flow turbomachine or radial-flow turbomachine. The flow machine of the present invention may equally be a screw pump.
The flow machine cited in this invention may also be arranged for measuring the throughput of an aggressive, radioactive or special-purity flow medium by especially inductive measurement of the rotational speed of the impeller allowing passage to the flow, where this speed is a measure of the throughput. In this particular application of the invention the benefits discussed above are achieved as well. Also the function of speed is independent of bearing friction which would vary with speed.